1st Grade Math Quiz: Understanding Teens

20 questions · exam conditions

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Understanding TeensQuestion 1 of 20

Chen has 1 group of 10 marbles and 4 marbles. 14 is 10 + .

1st Grade Math Quiz

1st Grade Math Quiz: Understanding Teens

Practice Understanding Teens in 1st Grade Math with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Understanding Teens, giving you a quick way to practice the rules, question types, and explanations that matter most for 1st Grade Math.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

Chen has 1 group of 10 marbles and 4 marbles. 14 is 10 + .

4 (correct answer)
10
14
40

Explanation: When you see a number like 14, it helps to break it apart into tens and ones. This is called place value. The number 14 has 1 ten and 4 ones, so you can write it as 14 = 10 + 4. Chen shows this perfectly: he has 1 group of 10 marbles (that's the ten) and 4 loose marbles (those are the ones). Putting them together, 10 + 4 = 14. So the blank must be filled with 4, since that's the leftover part after the group of ten. Now look at why the other choices don't work. Choosing 10 would give you 10 + 10 = 20, not 14 — you'd be adding two groups of ten instead of the loose marbles. Choosing 14 would give you 10 + 14 = 24, which is way too big; that mistakes the whole number for just the ones part. Choosing 40 would give you 10 + 40 = 50 — this comes from confusing the digit 4 (four ones) with 40 (four tens). A helpful trick: whenever a teen number is written as "10 + ," just look at the last digit of the teen number. In 14, the last digit is 4, so the answer is 4. This works for all teens: 13 is 10 + 3, 17 is 10 + 7, and so on. The ones digit always fills the blank!

Question 2

Look at 19. 19 is the same as 10 + .

8
9 (correct answer)
10
19

Explanation: When you see a two-digit number like 19, you can break it apart into tens and ones. This is called place value. The number 19 has 1 ten and 9 ones, so you can write it as 10 + 9. Think about it this way: start at 10, then count up until you reach 19. You'd say 11, 12, 13, 14, 15, 16, 17, 18, 19 — that's 9 more steps. So the missing number is 9, because 10 + 9 = 19. Now let's check why the other choices don't work. If you picked 8, you'd get 10 + 8 = 18, which is one too small. If you picked 10, you'd get 10 + 10 = 20, which is one too big. And if you picked 19, you'd get 10 + 19 = 29 — that's way too much, because you added the whole number 19 instead of just the ones part. Here's a handy trick to remember: for any teen number, the digit on the right tells you how many ones to add to 10. In 19, the right digit is 9, so the answer is 10 + 9. Try it with others: 15 is 10 + 5, and 13 is 10 + 3. Just look at that last digit!

Question 3

Look at 18. 18 is the same as 10 + .

7
8 (correct answer)
9
18

Explanation: This question is all about place value — understanding how a two-digit number can be broken apart into tens and ones. When you see a number like 18, think of it as having a "tens part" and a "ones part." The number 18 has a 1 in the tens place and an 8 in the ones place. That 1 in the tens place really means one group of ten, or 10. The 8 means 8 ones. So when you add them back together, you get: 10 + 8 = 18 That's why 8 is the missing number! You can also count up from 10: eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen — that's 8 numbers after 10. Now let's check the others. If you picked 7, that gives you 10 + 7 = 17, which is one too few. If you picked 9, that gives you 10 + 9 = 19, which is one too many. And 18 doesn't work at all, because 10 + 18 = 28 — you'd be adding way too much, since 18 is the whole number, not just the ones part. Study tip: For any "teen" number, the missing part after 10 is simply the last digit you see. In 18, the last digit is 8, so 18 is 10 + 8. Try it: 15 is 10 + 5, and 13 is 10 + 3. The ones digit is your answer every time!

Question 4

Jamal has 14 blocks. 14 is 1 ten and ones.

3
4 (correct answer)
5
10

Explanation: Whenever you see a number like 14 and are asked to break it into tens and ones, remember that each ten is a group of 10, and the ones are the leftover single blocks. This is called "place value," and it helps you understand what the digits in a number really mean. Look at the number 14. It has two digits: the 1 and the 4. The 1 is in the tens place, so it means 1 group of ten, which is 10 blocks. The 4 is in the ones place, so it means 4 single blocks. Put them together: 10 + 4 = 14. So 14 is 1 ten and 4 ones. Now let's check the other choices. If you picked 3 ones, that would give you 10 + 3 = 13, not 14 — that's one block too few. If you picked 5 ones, that would make 10 + 5 = 15, which is one block too many. And if you picked 10 ones, that would give you 10 + 10 = 20 — way too big, because you'd have two full tens, not one! A helpful trick: the ones digit of a "teen" number tells you the number of ones directly. In 14, the last digit is 4, so there are 4 ones. In 17, there'd be 7 ones, and so on. Just look at the last digit when the number is in the teens!

Question 5

Maya has 15. What is 15 made of?

1 ten and 5 ones (correct answer)
5 tens and 1 one
1 ten and 6 ones
15 ones

10 + 5 = 15

. This structure helps students understand place value and connects the teen number names to their composition. The question asks what the teen number 15 is made of. Choice A is correct because 1 ten plus 5 ones equals 15. Choice B is a common error where students reverse tens and ones (5 tens and 1 one instead of 1 ten and 5 ones). This happens because reversing digits is common (15 vs 51). To help students: Use base-10 blocks extensively—always show 1 ten-rod plus unit cubes for teens; connect number names to structure ('fif-teen' =

5 + 10

); practice building each teen number with 1 ten and ones repeatedly; emphasize ALL teen numbers have 1 ten, only the ones vary; use ten-frames with one full frame (the ten) and partial second frame (the ones); write equations (

10 + 5 = 15

); practice decomposing teens into

10 + \text{ones}

; compare teens to show same ten structure.

Question 6

Look at 12. How many tens are in 12?

0 tens
2 tens
1 ten (correct answer)
12 tens

Explanation: This question tests 1st grade understanding that teen numbers (11-19) are composed of 1 ten and ones (CCSS.1.NBT.2.b). All teen numbers—11, 12, 13, 14, 15, 16, 17, 18, and 19—have the same structure: exactly 1 ten plus some ones (between 1 and 9 ones). For example, 12 is made of 1 ten and 2 ones, which we can also write as 10 + 2 = 12. This structure helps students understand place value and connects the teen number names to their composition. The question asks for the number of tens in the teen number 12. Choice C is correct because all teen numbers contain 1 ten, and this one has 2 ones making it 12. Choice B is a common error where students say 2 tens or 0 tens instead of recognizing exactly 1 ten in all teens. This happens because understanding that 'twelve' means 2 beyond 10 requires explicit instruction. To help students: Use base-10 blocks extensively—always show 1 ten-rod plus unit cubes for teens; connect number names to structure ('twe-lve' relates to 2 + 10); practice building each teen number with 1 ten and ones repeatedly; emphasize ALL teen numbers have 1 ten, only the ones vary; use ten-frames with one full frame (the ten) and partial second frame (the ones); write equations (10 + 2 = 12); practice decomposing teens into 10 + ones; compare teens to show same ten structure.

Question 7

Ben counts $17$ blocks. He accidentally drops some blocks and now he has $1$ ten-block and $5$ single blocks left. How many blocks did Ben drop?

$2$ blocks because $17$ minus $15$ equals $2$ (correct answer)
$3$ blocks because $17$ minus $14$ equals $3$
$12$ blocks because $17$ minus $5$ equals $12$
$6$ blocks because $17$ minus $11$ equals $6$

Explanation: Ben originally had 17 blocks (1 ten and 7 ones). Now he has 1 ten-block and 5 single blocks, which equals 15 blocks total. So he dropped 17 - 15 = 2 blocks. Choice B miscounts the remaining blocks as 14. Choice C ignores the ten-block completely. Choice D miscounts the remaining blocks as 11.

Question 8

Emma counts her toy cars and finds she has $1$ group of $10$ cars and $7$ individual cars. Later, she finds $2$ more cars under her bed. How many cars does Emma have now, written as tens and ones?

$1$ ten and $7$ ones, which makes $17$ cars total
$1$ ten and $9$ ones, which makes $19$ cars total (correct answer)
$2$ tens and $7$ ones, which makes $27$ cars total
$1$ ten and $2$ ones, which makes $12$ cars total

Explanation: When you see a problem about tens and ones, you're working with place value - understanding that numbers can be broken down into groups of ten and leftover ones. Let's start with what Emma has:

1

group of

10

cars plus

7

individual cars. That gives her

10 + 7 = 17

cars total. Then she finds

2

more cars, so now she has

17 + 2 = 19

cars. Now we need to rewrite

19

in tens and ones. Since

19 = 10 + 9

, Emma has

1

ten and

9

ones, making

19

cars total. This matches answer choice B. Let's check why the other answers are wrong. Answer A (

1

ten and

7

ones =

17

) gives us Emma's original amount before she found the extra cars - this misses the step of adding the

2

cars she discovered. Answer C (

2

tens and

7

ones =

27

) incorrectly treats the

2

extra cars as

2

tens instead of

2

ones. Answer D (

1

ten and

2

ones =

12

) only counts the original ten plus the

2

new cars, forgetting about the original

7

individual cars. When solving tens and ones problems, always do your addition first to find the total number, then break that total back into groups of ten plus leftover ones. Don't try to work with tens and ones during the addition - it's easier to add regular numbers first.

Question 9

Jamal has 1 bundle of 10 sticks and 7 loose sticks. How many ones?

1
7 (correct answer)
17
8

Explanation: This question tests 1st grade understanding that teen numbers (

11-19

) are composed of 1 ten and ones (CCSS.1.NBT.2.b). All teen numbers—11, 12, 13, 14, 15, 16, 17, 18, and 19—have the same structure: exactly 1 ten plus some ones (between 1 and 9 ones). For example, 17 is made of 1 ten and 7 ones, which we can also write as

10 + 7 = 17

. This structure helps students understand place value and connects the teen number names to their composition. The scenario describes Jamal with 1 bundle of 10 sticks and 7 loose sticks, focusing on identifying the ones in a teen number. Choice B is correct because the 7 loose sticks represent the ones in 17. Choice C is a common error where students count the total instead of just the ones. To help students: Use base-10 blocks extensively—always show 1 ten-rod plus unit cubes for teens; connect number names to structure ('seven-teen' =

7 + 10

10 + 7 = 17

); practice decomposing teens into

10 + \text{ones}

; compare teens to show same ten structure.

Question 10

Sofia shows 1 ten-rod and 5 cubes. 1 ten and 5 ones makes .

6
10
15 (correct answer)
51

Explanation: Whenever you see ten-rods and cubes, remember that this is all about place value. A ten-rod is a bundle of 10 ones stuck together, and each single cube counts as just 1. To find the total, you add the tens and the ones. Here, Sofia has 1 ten-rod, which is worth 10, and 5 loose cubes, which are worth 5. Put them together: 10 + 5 = 15. That's why 15 is correct. Another way to think about it: the "1 ten" goes in the tens place and the "5 ones" goes in the ones place, spelling out 15. The choice 6 comes from adding the number of rods and cubes (1 + 5) instead of their values — but a rod isn't worth 1, it's worth 10. The choice 10 only counts the ten-rod and forgets the 5 cubes completely. The choice 51 is a place-value flip: it puts the 5 in the tens place and the 1 in the ones place, reversing the order. Always keep tens first, ones second. A helpful trick: read it left to right just like you say it — "one ten, five ones" becomes the digits 1 then 5, giving 15. When a question mixes rods and cubes, count how many tens and how many ones, then place the tens digit before the ones digit.

Question 11

Maya has 1 bundle of 10 straws and 2 loose straws. 12 is 1 ten and ones.

1
2 (correct answer)
3
10

Explanation: Whenever you see a two-digit number, remember that it's made of two parts: tens and ones. The first digit tells you how many groups of ten you have, and the second digit tells you how many extra single (loose) ones are left over. Thinking about bundles of straws is a perfect way to picture this! Look at the number 12. The digit in the tens place is 1, which means 1 bundle of ten. The digit in the ones place is 2, which means 2 loose ones. This matches Maya exactly: she has 1 bundle of 10 straws and 2 loose straws. So 12 = 1 ten + 2 ones, making 2 the right answer. The choice 1 is wrong because 1 counts the bundle of ten, not the loose straws — you'd be repeating the tens digit instead of finding the ones. The choice 3 is wrong because Maya only has 2 loose straws, not 3; counting an extra straw would make the number 13, not 12. The choice 10 is wrong because 10 is the size of the bundle, not the number of loose ones — you can never have 10 ones left over, since 10 ones would just make another bundle of ten. A helpful trick: for any two-digit number, just read the digits! The left digit = number of tens, and the right digit = number of ones. In 12, the "2" is sitting right there telling you the answer.

Question 12

Look at the number 18. How many tens are in 18?

0
2
8
1 (correct answer)

10 + 8 = 18

. This structure helps students understand place value and connects the teen number names to their composition. The question asks for the number of tens in 18, focusing on the place value component of a teen number. Choice D is correct because all teen numbers contain exactly 1 ten. Choice B is a common error where students say 2 tens, perhaps confusing with 20 or miscounting. To help students: Use base-10 blocks extensively—always show 1 ten-rod plus unit cubes for teens; connect number names to structure ('eigh-teen' = 8 + 10); practice building each teen number with 1 ten and ones repeatedly; emphasize ALL teen numbers have 1 ten, only the ones vary; use ten-frames with one full frame (the ten) and partial second frame (the ones); write equations (

10 + 8 = 18

); practice decomposing teens into 10 + ones; compare teens to show same ten structure.

Question 13

Look at 1 ten-rod and 3 cubes. 1 ten and ones is 13.

2
3 (correct answer)
4
10

Explanation: When you see a ten-rod and some loose cubes, you're working with place value. A ten-rod is a stick made of 10 little cubes joined together, so it always equals 10 ones. The loose cubes are just single ones. To find the total, you add the ten to the number of extra cubes. Here you have 1 ten-rod, which is 10, and 3 loose cubes. Count the cubes: 1, 2, 3 — that's 3 ones. So the sentence reads "1 ten and 3 ones is 13," because 10 + 3 = 13. That's why the answer is 3. Now think about why the others don't fit. Choosing 2 would mean you only counted 2 cubes, giving 10 + 2 = 12 — you missed one cube. Choosing 4 would mean you counted an extra cube you don't have, since 10 + 4 = 14. Choosing 10 is a trap: you might think a ten-rod means you write 10 for the ones, but the ten is already counted separately — the ones are only the loose cubes, and there are just 3 of them. A helpful strategy: whenever you see a number like 13, remember the first digit tells the tens and the last digit tells the ones. In 13, the 1 means 1 ten-rod and the 3 means 3 loose cubes. Match each digit to the correct part, and you'll get these questions right every time.

Question 14

Emma has 14 sticks: 1 bundle of 10 and 4 loose. How many ones are in 14?

1
4 (correct answer)
10
14

Explanation: The number 14 has 1 ten and 4 ones, so there are 4 ones. 1 is far too few to match the ones digit of 14. 10 is the value of the tens bundle, not the ones. 14 repeats the whole number instead of just the ones part. Only 4 correctly shows the ones in 14.

Question 15

The ten-frames show 10 counters and 2 more. What teen number is shown?

12 (correct answer)
13
18
11

Explanation: This question tests 1st grade understanding that teen numbers (11-19) are composed of 1 ten and ones (CCSS.1.NBT.B.2.b). All teen numbers—11, 12, 13, 14, 15, 16, 17, 18, and 19—have the same structure: exactly 1 ten plus some ones (between 1 and 9 ones). For example, 12 is made of 1 ten and 2 ones, which we can also write as

10 + 2 = 12

. This structure helps students understand place value and connects the teen number names to their composition. The stimulus shows ten-frames with 10 counters and 2 more. Choice A is correct because 1 ten plus 2 ones equals 12. Choice C is a common error where students reverse tens and ones or think of 2 tens and 10 ones, which happens because reversing digits is common (12 vs 21). To help students: Use base-10 blocks extensively—always show 1 ten-rod plus unit cubes for teens; connect number names to structure ('twe-lve' relates to 2 + 10); practice building each teen number with 1 ten and ones repeatedly; emphasize ALL teen numbers have 1 ten, only the ones vary; use ten-frames with one full frame (the ten) and partial second frame (the ones); write equations (

10 + 2 = 12

); practice decomposing teens into 10 + ones; compare teens to show same ten structure.

Question 16

Look at the base-ten blocks shown in the figure. Alex removes $4$ unit blocks from this collection. Which number sentence shows what Alex has left?

$16 - 4 = 12$ , which is $1$ ten and $2$ ones (correct answer)
$16 - 4 = 12$ , which is $0$ tens and $12$ ones
$10 - 4 = 6$ , which is $0$ tens and $6$ ones
$6 - 4 = 2$ , which is $0$ tens and $2$ ones

Explanation: The figure shows 16 blocks total (1 ten-block and 6 unit blocks). Removing 4 unit blocks gives 16 - 4 = 12, which is 1 ten and 2 ones. Choice B has the correct calculation but doesn't use place value properly. Choice C only counts the unit blocks initially. Choice D only considers the remaining unit blocks after the ten-block.

Question 17

Look at the number line. Amy started at $16$ and moved backward $6$ ones. Where did she end up?

At $10$ , which is $1$ ten and $0$ ones (correct answer)
At $22$ , which is $2$ tens and $2$ ones
At $12$ , which is $1$ ten and $2$ ones
At $14$ , which is $1$ ten and $4$ ones

Explanation: Starting at 16 (1 ten and 6 ones) and moving backward 6 ones: 16 - 6 = 10, which is 1 ten and 0 ones. Choice B shows moving forward instead of backward. Choice C shows subtracting only 4 instead of 6. Choice D shows subtracting only 2 instead of 6.

Question 18

Carlos has 1 group of 10 shells and 8 shells. 1 ten and 8 ones makes .

9
10
18 (correct answer)
81

Explanation: Whenever you see a question about "tens and ones," think of it as building a two-digit number from place-value blocks. The tens tell you how many groups of 10 you have, and the ones tell you how many single units you have. When you put them together, the tens go in the left spot (the tens place) and the ones go in the right spot (the ones place). Carlos has 1 group of 10 shells, which is just 10, plus 8 single shells. Adding those together: 10 + 8 = 18. You can also read it straight from the place values: 1 ten and 8 ones make the number 18 — the "1" sits in the tens place and the "8" sits in the ones place. The choice 9 is wrong because it looks like you added 1 + 8 and forgot that the "1" actually means one ten, not one one. The choice 10 is a trap because it only counts the group of ten and ignores the 8 loose shells. The choice 81 is wrong because the digits are swapped — that would mean 8 tens and 1 one, but Carlos only has 1 ten and 8 ones, so the order matters. A helpful tip: always write the tens number first and the ones number second, like snapping two puzzle pieces together — "1 ten and 8 ones" becomes "1, then 8" → 18. Watch out for questions that try to flip the digits!

Question 19

Look at 13. 13 is 1 ten and ones.

2
3 (correct answer)
4
10

Explanation: When you see a two-digit number like 13, remember that it's built from tens and ones. The number on the left tells you how many groups of ten you have, and the number on the right tells you how many extra ones are left over. Break 13 apart: it has 1 group of ten, which is 10. To find the ones, ask yourself, "How many more do I need to get from 10 to 13?" Counting up—10, 11, 12, 13—that's 3 more. So 13 is 1 ten and 3 ones. You can also just look at the digit in the ones place: the 3 in 13 tells you directly! Now let's check why the others don't work. Saying 13 is 1 ten and 2 ones would only give you 10 + 2 = 12, which is too small by one. Saying 1 ten and 4 ones gives 10 + 4 = 14, which is too big by one. Saying 1 ten and 10 ones gives 10 + 10 = 20—that's way too many, and 10 ones would actually make a whole new ten, not stay as loose ones. A handy trick to remember: in any two-digit number, the second digit is the number of ones. So in 13, the 1 means "1 ten" and the 3 means "3 ones." Practice reading numbers this way and place value will become quick and easy!

Question 20

Amir built 1 ten and 2 ones. It makes .

3
10
12 (correct answer)
21

Explanation: When you see "tens and ones," think about place value. A number has two parts: how many groups of ten it holds, and how many single ones are left over. Each "ten" is worth 10, and each "one" is worth 1. Amir built 1 ten and 2 ones. Start with the ten, which equals 10. Then add the 2 ones, which equals 2. Put them together: 10 + 2 = 12. You can also read it directly — the tens digit is 1 and the ones digit is 2, so the number is 12. The answer 3 comes from adding the two numbers you see (1 and 2) as if they were both ones, ignoring that the "1" means one ten. The answer 10 only counts the ten and forgets to add the 2 ones on top of it. The answer 21 has the right digits but flipped — that would be 2 tens and 1 one, which is a different amount (20 + 1). Order matters: the tens always come first, then the ones. A helpful trick: line the words up with the number. "1 ten" writes the 1 in the tens spot, and "2 ones" writes the 2 in the ones spot, giving you 1‑2 → 12. Always keep tens on the left and ones on the right, and never just smash the two digits together by adding them.